Image display system and method

ABSTRACT

An image display system comprises a first liquid crystal projector which projects a counterclockwise-rotating, circularly polarized light beam to form an image containing specific visual information on a screen and a second liquid crystal projector which projects a clockwise-rotating, circularly polarized light beam to form a white image on the same screen. When viewed with the naked eye, a combination of the two images projected on the screen appears totally white. A viewer wearing a dedicated viewing device equipped with an optical filter which allows counterclockwise-rotating, circularly polarized light to pass through can selectively see the image projected by the first liquid crystal projector.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image display system which iscapable of displaying an image on a screen in such a manner that theimage can be observed only by a specific viewer or viewers and moreparticularly to such type of display system that can be made use of whenit is necessary to convey image information to a particular person orpersons in a public institution. The invention also relates to an imagedisplay method using such a system.

2. Description of the Related Art

Display systems represented by liquid crystal devices are known. In thecase of such display systems, it is usual that the displayed images arewatched by a plurality of viewers simultaneously.

However, where an image is displayed in a public institution forbusiness or educational purposes, there is a case in which it is desiredto convey selectively specific pieces of image information to specificviewers only but the conventional display systems can not serve suchpurposes.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide an imagedisplay system having a structure such that a plurality of images can beindividually observed by a plurality of viewers, and also to provide animage display method using such a system.

According to a first aspect of the invention, the image display systemis so constructed that a first image having a first state ofpolarization and a second image having a second state of polarizationare projected with one image superimposed on another, wherein the firstimage is entirely white.

According to a second aspect of the invention, the image display systemis so constructed that a first image having a first state ofpolarization and a second image having a second state of polarizationare projected with one image superimposed on another, wherein the secondimage contains specific information to be displayed and the first imageforms a white pattern to cover a specific part of or the whole of thesecond image.

According to a third aspect of the invention, the image display systemis so constructed that a first image having a first state ofpolarization and a second image which is time-division displayed and hasa second state of polarization are projected with one image superimposedon another, wherein the second image is intended to display specificinformation and the first image forms a white pattern to cover aspecific part of or the whole of the second image.

In any of the image display systems thus constructed, the first andsecond images may be circularly polarized with clockwise rotation andwith counterclockwise rotation, respectively, or vice versa.

Alternatively, the first and second images may be linearly polarizedwith their planes of polarization intersecting at right angles with eachother.

In another alternative approach, the first and second images arecircularly polarized in opposite rotating directions, and their rotatingdirections are alternately reversed in successive time frames under thetime-division display scheme. This approach enables a viewer toselectively observe the second image without being disturbed by thewhite pattern formed by the first image.

In one method of the invention for providing on-screen visual display, afirst image having a first state of polarization and a second imagehaving a second state of polarization are projected with one imagesuperimposed on another, the first image being entirely white, wherein aviewer looking through an optical filter which selectively allows lightof the second state of polarization to pass through can see the secondimage.

In another method of the invention for providing on-screen visualdisplay, a first image having a first state of polarization and a secondimage having a second state of polarization are projected with one imagesuperimposed on another, the first image forming a white pattern just tocover such part of the second image that should be hidden from view ofunspecified viewers, wherein a viewer looking through an optical filterwhich selectively allows light of the second state of polarization topass through can see the second image.

According to a fourth aspect of the invention, the image display systemfor projecting a plurality of images on a screen with one imagesuperimposed on another comprises a first liquid crystal projector foralternately projecting mutually differing first and second images havinga first state of polarization in successive time frames in accordancewith a time-division display scheme, a second liquid crystal projectorfor projecting a white image having a second state of polarization whichdiffers from the first state of polarization, a first viewing deviceassigned to a first viewer incorporating a first liquid crystal shutterwhich opens and closes in synchronism with time-division displayoperation of the first liquid crystal projector to selectively allow thefirst image to pass through and a first optical filter which allows theimage having the first state of polarization to pass through, and asecond viewing device assigned to a second viewer incorporating a secondliquid crystal shutter which opens and closes in synchronism with thetime-division display operation of the first liquid crystal projector toselectively allow the second image to pass through and a second opticalfilter which allows the image having the first state of polarization topass through, whereby the first viewer wearing the first viewing devicecan selectively see the first image and the second viewer wearing thesecond viewing device can selectively see the second image, whileviewers not wearing such a viewing device can only see the white image.

According to a fifth aspect of the invention, the image display systemfor projecting a plurality of images on a screen with one imagesuperimposed on another comprises a first liquid crystal projector foralternately projecting images for right and left eyes in successive timeframes in accordance with a time-division display scheme, the imageshaving a first state of polarization, a second liquid crystal projectorfor projecting a white image having a second state of polarization whichdiffers from the first state of polarization, and a viewing deviceassigned to a viewer incorporating a first liquid crystal shutter which,provided at the right-eye side of the viewing device, opens and closesin synchronism with time-division display operation of the first liquidcrystal projector to selectively allow the image for the right eye topass through, a second liquid crystal shutter which, provided at theleft-eye side of the viewing device, opens and closes in synchronismwith the time-division display operation of the first liquid crystalprojector to selectively allow the image for the left eye to passthrough, a first optical filter which, provided at the right-eye side ofthe viewing device, allows the image having the first state ofpolarization to pass through, and a second optical filter which,provided at the left-eye side of the viewing device, allows the imagehaving the first state of polarization to pass through, whereby theviewer wearing the viewing device can selectively see athree-dimensional image, while viewers not wearing such a viewing devicecan only see the white image.

According to a sixth aspect of the invention, the image display systemcomprises a liquid crystal panel including a plurality of active matrixregions and common peripheral circuits for controlling horizontal and/orvertical scanning operation in the active matrix regions, the activematrix regions and the peripheral circuits being formed on a singlesubstrate, a polarizer for giving a first state of polarization to atleast one of images generated by the active matrix regions, a polarizerfor giving a second state of polarization to an image other than theimages to which the first state of polarization is given, and aprojector for projecting the images generated in the active matrixregions of the liquid crystal panel on a screen with one imagesuperimposed on another, wherein at least one of the images generated bythe active matrix regions is entirely white.

According to a seventh aspect of the invention, the image display systemcomprises a liquid crystal panel including a plurality of active matrixregions and common peripheral circuits for controlling horizontal and/orvertical scanning operation in the active matrix regions, the activematrix regions and the peripheral circuits being formed on a singlesubstrate, a polarizer for giving a first state of polarization to atleast one of images generated by the active matrix regions, a polarizerfor giving a second state of polarization to an image other than theimages to which the first state of polarization is given, and aprojector for projecting the images generated in the active matrixregions of the liquid crystal panel on a screen with one imagesuperimposed on another, wherein at least one of the images generated bythe active matrix regions forms a white pattern just to cover such partof the other images that should be hidden from view.

In either of the image display systems comprising the aforementionedliquid crystal panel, the first and second states of polarization may becircular polarization with opposite rotating directions, or linearpolarization with their planes of polarization intersecting at rightangles to each other.

In one preferred embodiment, the first and second liquid crystalprojectors project respective images on a common screen. The imageprojected by the second liquid crystal projector is circularly polarizedwith clockwise rotation as the image passes through a polarizing plateand a quarter-wave plate. On the other hand, the image projected by thefirst liquid crystal projector is circularly polarized withcounterclockwise rotation as the image passes through a polarizingplate, a π-cell employing a liquid crystal cell for rotating the planeof polarization by 90 degrees and a quarter-wave plate.

The clockwise-rotating, circularly polarized image An projected by thesecond liquid crystal projector and the counterclockwise-rotating,circularly polarized image B_(n) projected by the first liquid crystalprojector are therefore superimposed on the same screen.

In this embodiment, the image A_(n) projected by the second liquidcrystal projector is blank, or entirely white, while the image B_(n)projected by the first liquid crystal projector contains specific visualinformation.

When viewed with the naked eye, a combination of the white image A_(n)and the image B_(n) containing the specific visual information projectedon the screen appears totally white. This is because the image B_(n) ismasked by the white image A_(n).

Any viewer who wished to see, or need to see, the visual informationcontained in the image B_(n) should wear a dedicated viewing deviceequipped with an optical filter which selectively allowscounterclockwise-rotating, circularly polarized light emitted by thefirst liquid crystal projector to pass through and look at the screenfrom the opposite side of the projectors. (It is to be noted that therotating direction of the circularly polarized light is apparentlyreversed when viewed from the opposite side of the projectors.)

With this arrangement, it is possible to completely hide away the imageB_(n) from view of those people who are not willing to see, or need notsee, the image Bn, just allowing specific viewers to see it. Theembodiment may be modified such that the image A_(n) forms a particularwhite pattern to mask a specific part of the image B_(n). This makes itpossible to hide specific pieces of visual information from public view.

The arrangement of the invention can be used for conveying visualinformation to concerned personnel only through a video screen which canbe seen by the general public. Potential applications of this kind wouldbe found in various industrial fields including the use in public spacesand buildings.

The invention also makes it possible to present a three-dimensionalimage to specific viewers by using a time-division display technique.

According to the invention, each image display system employs anintegrated liquid crystal panel to produce individual images. The use ofsuch integrated liquid crystal panels serves to offer such advantages ascompact design, improved productivity and higher reliability of theimage display systems.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing the construction of an imagedisplay system which can selectively visualize a specific imageaccording to a first embodiment of the invention;

FIG. 2 is an operational timing chart of the image display system ofFIG. 1;

FIG. 3 is a schematic diagram showing the construction of an imagedisplay system which can selectively visualize a specific imageaccording to a second embodiment of the invention;

FIG. 4 is an operational timing chart of the image display system ofFIG. 3;

FIG. 5 is a schematic diagram showing the construction of an imagedisplay system which can selectively visualize a specific imageaccording to a third embodiment of the invention;

FIG. 6 is an operational timing chart of the image display system ofFIG. 5;

FIG. 7 is a schematic diagram showing the construction of an imagedisplay system which can selectively visualize a specific imageaccording to a fourth embodiment of the invention;

FIG. 8 is an operational timing chart of the image display system ofFIG. 7;

FIG. 9 is a schematic diagram showing the construction of an imagedisplay system which can selectively visualize a specific imageaccording to a fifth embodiment of the invention;

FIG. 10 is an operational timing chart of the image display system ofFIG. 9;

FIG. 11 is a circuit diagram showing a general configuration of anintegrated liquid crystal panel employed in a sixth embodiment of theinvention;

FIG. 12 is a diagram showing the construction of a projection-type imagedisplay system employing the liquid crystal panel depicted in FIG. 11;

FIG. 13 is a timing chart describing operation for presenting imageswith the image display system of FIG. 12; and

FIG. 14 is a circuit diagram showing a general configuration of anintegrated liquid crystal panel employed in a seventh embodiment of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

FIG. 1 is a schematic diagram showing the construction of an imagedisplay system according to a first embodiment of the invention,comprising a pair of liquid crystal projectors 11 and 12 which areassociated with such devices that cause light beams emitted by therespective projectors 11 and 12 to be circularly polarized in oppositerotating directions.

The liquid crystal projectors 11 and 12 of this embodiment are identicalto each other and emit light beams polarized in the same direction.Images projected by them may either be monochrome or in color. Theliquid crystal projector 11 which projects one image on a screen 17 isassociated with a polarizing plate 13 and a quarter-wave plate 15 toproduce a clockwise-rotating, circularly polarized beam, whereas theliquid crystal projector 12 which projects another image on the screen17 is associated with a polarizing plate 18, a liquid crystal cell 14for rotating the plane of polarization by 90 degrees and a quarter-waveplate 16 to produce a counterclockwise-rotating, circularly polarizedbeam.

The image projected by the liquid crystal projector 11 according to atiming chart shown in FIG. 2 is blank, or entirely white, while theimage projected by the liquid crystal projector 12 contains specificimage elements.

A group of viewers wear viewing devices incorporating filters whichallow only the clockwise-rotating, circularly polarized beam emittedfrom the liquid crystal projector 11 to pass through. These viewerswatch the screen 17 from the opposite side of the projectors 11 and 12and can see the image A_(n) produced by the clockwise-rotating,circularly polarized beam. This is because thecounterclockwise-rotating, circularly polarized beam for producing theentirely white image can not pass through each viewing device.

The screen 17 looks totally white for those who are not wearing suchviewing devices. This makes it possible to hide away a particular imagefrom the sight of a second group of viewers for whom the image is notrequired.

The present embodiment is based on a combination of the clockwise- andcounterclockwise-rotating, circularly polarized beams in operation. Analternative approach to selective visualization of projected images isto use a combination of different states of polarization, which involvestwo linearly polarized light beams, each polarized at right angles tothe other. This alternative approach is advantageous in that the meansfor polarization and selective visualization can be much simplified.

The white image represented by B_(n) in FIG. 2 is not necessarilyrequired to cover the whole screen area. It may cover only such an areawhere the image A_(n) is projected, or particular portions of the imageA_(n) to hide away specific image elements.

Second Embodiment

A second embodiment of the invention described below is based on atime-division display technique, in which two different images A and Bare alternately presented on a single screen 37 in successive timeframes. Although a viewer properly equipped with dedicated viewing meanscan see one of these images, nothing but an entirely white image isvisible to the naked eye.

FIG. 3 is a schematic diagram showing the construction of an imagedisplay system according to the second embodiment, comprising a pair ofliquid crystal projectors 21 and 22. In FIG. 3, designated by thenumeral 23 is a polarizing plate, designated by the numeral 24 is aπ-cell and designated by the numeral 25 is a quarter-wave plate. Also,designated by the numeral 38 is a polarizing plate, designated by thenumeral 39 is a π-cell and designated by the numeral 40 is aquarter-wave plate.

In this embodiment, the π-cells 24 and 39 are configured to operate inmutually reversed phases. More specifically, the π-cell 39 is set to anOFF state when the π-cell 24 is in an ON state. Conversely, the π-cell39 is set to an ON state when the π-cell 24 is in an OFF state.

Designated by the numeral 26 is a controller for controlling the π-cells24 and 39 and for opening and closing liquid crystal shutters 29 and 31of a viewing device 27 as well as liquid crystal shutters 33 and 35 of aviewing device 28 in synchronism with the operation of the π-cells 24and 39. In this embodiment, the images projected by the liquid crystalprojectors 21 and 22 are superimposed on each other on the screen 37.

A light beam emitted by the liquid crystal projector 21 is circularlypolarized as it passes through the polarizing plate 23, π-cell 24 andquarter-wave plate 25. More specifically, a clockwise-rotating,circularly polarized beam is produced when the π-cell 24 is ON, whereasa counterclockwise-rotating, circularly polarized beam is produced whenthe π-cell 24 is OFF.

Designated by the numerals 30, 32, 34 and 36 are optical filters whichallow only such light beams that have specific states of circularpolarization to pass through. The optical filters 30 and 32 selectivelyallow clockwise-rotating, circularly polarized extraneous light to passthrough, whereas the optical filters 34 and 36 selectively allowcounterclockwise-rotating, circularly polarized extraneous light to passthrough.

A relationship between the images passing through the π-cell 24 andstates of the individual liquid crystal shutters 29, 31, 33 and 35 isdepicted in an operational timing chart shown in FIG. 4. In thisembodiment, the light beam emitted from the liquid crystal projector 21is divided in time, or multiplexed, to alternately project the twodifferent images A and B.

As shown in FIG. 4, the liquid crystal projector 22 emits light forprojecting an entirely white image. In the image display system of thisembodiment which is operated as shown in FIG. 4, a viewer wearing theviewing device 27 can selectively see the image A_(n) produced by theclockwise-rotating, circularly polarized beam, whereas a viewer wearingthe viewing device 28 can selectively see the image B_(n) produced bythe counterclockwise-rotating, circularly polarized beam.

Since the rotating direction of polarization of the light beam emittedby the liquid crystal projector 22 for producing the entirely whiteimage is opposite to that of the light beam for producing the imagesA_(n) and B_(n), the entirely white image projected by the liquidcrystal projector 22 does not affect the viewer wearing the viewingdevice 27 or 28.

On the other hand, a viewer not wearing the viewing device 27 or 28 cansee nothing but the entirely white image projected by the liquid crystalprojector 22 because the images projected by the liquid crystalprojector 21 are completely masked by the white image.

According to the construction of this embodiment, it is possible toselectively visualize the image A or B to the viewer wearing thededicated viewing device 27 or 28, while those not wearing such viewingdevices can not see any meaningful images.

Third Embodiment

A third embodiment of the invention described below is characterized inthat it allows a specific viewer to see a three-dimensional image whilepresenting an entirely white image to other viewers.

FIG. 5 is a schematic diagram showing the construction of an imagedisplay system according to the third embodiment, in which imagesprojected by liquid crystal projectors 42 and 43 are superimposed on oneanother on a screen 52. Although a viewer looking at the screen 52 withthe naked eye can see only a totally white image, a viewer wearing adedicated viewing device 41 can see a three-dimensional image.

The liquid crystal projector 42 shown in FIG. 5 alternately emits lightwaves for producing an image A for the right eye and an image B for theleft eye on the screen 52 in accordance with a time-division schemeshown in FIG. 6. These images pass through a polarizing plate 44, aπ-cell 45 and a quarter-wave plate 46 and are projected onto the screen52.

ON and OFF states of the π-cell 45 are controlled by a controller 47 inaccordance with the time-division scheme shown in FIG. 6. Althoughincident light passes through the π-cell 45 without any change when theπ-cell 45 is in an OFF state, a vertically polarized component of theincident light passing through π-cell 45 is rotated by 90 degrees whenit is set to an ON state.

On the other hand, a light beam emitted from the liquid crystalprojector 43 is circularly polarized as it passes through a polarizingplate 53, a π-cell 54 and a quarter-wave plate 55. In this embodiment,the π-cells 45 and 54 are configured to operate in mutually reversedphases. More specifically, the π-cell 54 is set to an OFF state when theπ-cell 45 is in an ON state. Conversely, the π-cell 54 is set to an ONstate when the π-cell 45 is in an OFF state. This reverse phaseoperation of the two π-cells 45 and 54 is controlled by the controller47.

The controller 47 also controls open/close operation of two liquidcrystal shutters 48 and 49. Referring to FIG. 5, designated by thenumerals 50 and 51 are optical filters which allow light beamscircularly polarized in mutually opposite rotating directions to passthrough. In this embodiment, their optical characteristics are set suchthat the optical filter 50 selectively allows the image A for the righteye to pass through while the optical filter 51 selectively allows theimage B for the left eye to pass through, as shown in FIG. 6.

As shown in the operational timing chart of FIG. 6, the image A entersthe right eye of the viewer wearing the viewing device 41 while theimage B enters the left eye of the same viewer. As a result, it seemsfor the viewer as if a three-dimensional image is presented on thescreen 52.

The entirely white image projected by the liquid crystal projector 43 iscircularly polarized in opposite directions with respect to the images Aand B which alternately enter the viewer's right and left eyes throughthe viewing device 41 in successive time frames in the time-divisionscheme. Therefore, the white image projected by the liquid crystalprojector 43 is almost completely cut off by the viewing device 41 sothat the effect of the white image on the viewer who sees thethree-dimensional image is practically negligible.

On the other hand, a viewer watching the screen 52 with the naked eyecan only see the totally white image. This means that the image displaysystem of this embodiment makes it possible to enable a specific viewerto see a three-dimensional image while presenting the entirely whiteimage, containing no visual information, to all other viewers.

Fourth Embodiment

Like the second embodiment, a fourth embodiment of the inventiondescribed below is based on the time-division display technique, inwhich two different images A and B are alternately presented on a singlescreen 76 in successive time frames. Although a viewer properly equippedwith dedicated viewing means can see one of these images, nothing but atotally white image is visible to the naked eye.

FIG. 7 is a schematic diagram showing the construction of an imagedisplay system according to the fourth embodiment, comprising a pair ofliquid crystal projectors 61 and 62. In FIG. 7, designated by thenumeral 63 is a polarizing plate and designated by the numeral 64 is aquarter-wave plate. Also, designated by the numeral 77 is a polarizingplate and designated by the numeral 78 is a quarter-wave plate.

Designated by the numeral 65 is a controller for controlling open/closeoperations of liquid crystal shutters 68 and 70 of a viewing device 66as well as liquid crystal shutters 72 an 74 of a viewing device 67 insynchronism with image display operation. In this embodiment, the imagesprojected by the liquid crystal projectors 61 and 62 are superimposed oneach other on the screen 76.

A light beam emitted by the liquid crystal projector 61 is circularlypolarized as it passes through the polarizing plate 63 and quarter-waveplate 64.

Designated by the numerals 69, 71, 73 and 75 are optical filters whichallow only such light beams that have specific states of circularpolarization to pass through. The optical filters 69 and 71 selectivelyallow counterclockwise-rotating, circularly polarized extraneous lightto pass through. Also, the optical filters 73 and 75 selectively allowcounterclockwise-rotating, circularly polarized extraneous light to passthrough.

A relationship among projection images and states of the individualliquid crystal shutters 68, 70, 72 and 74 is depicted in an operationaltiming chart shown in FIG. 8. In this embodiment, the light beam emittedfrom the liquid crystal projector 61 is divided in time, or multiplexed,to alternately project the two different images A and B.

As shown in FIG. 8, the liquid crystal projector 62 emits light forprojecting an entirely white image. In the image display system of thisembodiment which is operated as shown in FIG. 8, a viewer wearing theviewing device 66 can selectively see the image An produced by thecounterclockwise-rotating, circularly polarized beam, whereas a viewerwearing the viewing device 67 can selectively see the image B_(n)produced by the counterclockwise-rotating, circularly polarized beam.

Since the rotating direction of polarization of the light beam emittedby the liquid crystal projector 62 for producing the entirely whiteimage is clockwise, which is opposite to that of the light beam forproducing the images A_(n) and B_(n), the entirely white image projectedby the liquid crystal projector 62 does not affect the viewer wearingthe viewing device 66 or 67.

On the other hand, a viewer not wearing the viewing device 66 or 67 cansee nothing but the entirely white image projected by the liquid crystalprojector 62 because the images projected by the liquid crystalprojector 61 are completely masked by the white image.

Although the light beam emitted by the liquid crystal projector 61 forprojecting the images A_(n) and B_(n) is circularly polarized withcounterclockwise rotation while the light beam emitted by the liquidcrystal projector 62 for projecting the entirely white image iscircularly polarized with clockwise rotation in this embodiment, theinvention is not limited to this arrangement. It may be modified in sucha way that the light beam emitted by the liquid crystal projector 61 iscircularly polarized with clockwise rotation and the light beam emittedby the liquid crystal projector 62 is circularly polarized withcounterclockwise rotation.

According to the construction of this embodiment, it is possible toselectively visualize the image A or B to the viewer wearing thededicated viewing device 66 or 67, while those not wearing such viewingdevices can not see any meaningful images. Furthermore, this embodimentmakes it possible to reduce the loss of image brightness compared to thesecond embodiment by eliminating π-cells.

Fifth Embodiment

Like the third embodiment, a fifth embodiment of the invention describedbelow is characterized in that it allows a specific viewer to see athree-dimensional image while presenting an entirely white image toother viewers.

FIG. 9 is a schematic diagram showing the construction of an imagedisplay system according to the fifth embodiment, in which imagesprojected by liquid crystal projectors 81 and 82 are superimposed on oneanother on a screen 90. Although a viewer looking at the screen 90 withthe naked eye can see only a totally white image, a viewer wearingdedicated viewing device 80 can see a three-dimensional image.

The liquid crystal projector 81 shown in FIG. 9 alternately emits lightwaves for producing an image L_(n) for the left eye and an image R_(n)for the right eye on the screen 90 in accordance with a time-divisionscheme shown in FIG. 10. These images pass through a polarizing plate 83and a quarter-wave plate 84 and are projected onto the screen 90.

A light beam emitted from the liquid crystal projector 82 is circularlypolarized as it passes through a polarizing plate 91 and a quarter-waveplate 92.

Designated by the numeral 85 is a controller for controlling open/closeoperations of liquid crystal shutters 86 and 87 of the viewing device 80in synchronism with image display operation. In this embodiment, theimages projected by the liquid crystal projectors 81 and 82 aresuperimposed on each other on the screen 90.

Designated by the numerals 88 and 89 are optical filters which allowonly such light beams that have specific states of circular polarizationto pass through. The optical filters 88 and 89 of this embodimentselectively allow counterclockwise-rotating, circularly polarizedextraneous light to pass through.

As shown in the operational timing chart of FIG. 10, the image L_(n)enters the left eye of the viewer wearing the viewing device 80 whilethe image R_(n) enters the right eye of the same viewer. As a result, itseems for the viewer as if a three-dimensional image is presented on thescreen 90.

The entirely white image projected by the liquid crystal projector 82 iscircularly polarized with clockwise rotation, which is opposite to therotating direction of polarization (counterclockwise) of the imagesL_(n) and R_(n) alternately entering the viewer's right and left eyes.Therefore, the white image projected by the liquid crystal projector 82is almost completely cut off by the viewing device 80 so that the effectof the white image on the viewer who sees the three-dimensional image ispractically negligible.

On the other hand, a viewer watching the screen 90 with the naked eyecan only see the entirely white image. The image display system of thisembodiment makes it possible to enable a specific viewer to see athree-dimensional image while presenting the entirely white image,containing no visual information, to other viewers who looks at thescreen 90 with the naked eye.

Although the light beam emitted by the liquid crystal projector 81 forprojecting the images L_(n) and R_(n) is circularly polarized withcounterclockwise rotation while the light beam emitted by the liquidcrystal projector 82 for projecting the entirely white image iscircularly polarized with clockwise rotation in this embodiment, theinvention is not limited to this arrangement. It may be modified in sucha way that the light beam emitted by the liquid crystal projector 81 iscircularly polarized with clockwise rotation and the light beam emittedby the liquid crystal projector 82 is circularly polarized withcounterclockwise rotation.

This embodiment makes it possible to reduce the loss of image brightnesscompared to the third embodiment by eliminating π-cells.

Sixth Embodiment

FIG. 11 is a circuit diagram showing a general configuration of anintegrated liquid crystal panel 207 employed in a sixth embodiment ofthe invention. As shown in FIG. 11, the integrated liquid crystal panel207 comprises active matrix regions 101 to 104, a horizontal scanningcontrol circuit 105 for controlling horizontal scanning operation inthese active matrix regions 101-104, a vertical scanning control circuit106 for controlling vertical scanning operation in the active matrixregion 101, a vertical scanning control circuit 107 for controllingvertical scanning operation in the active matrix region 102, a verticalscanning control circuit 108 for controlling vertical scanning operationin the active matrix region 103, and a vertical scanning control circuit109 for controlling vertical scanning operation in the active matrixregion 104.

All these circuit elements including the active matrix regions 101-104,the horizontal scanning control circuit 105 and the vertical scanningcontrol circuits 106-109 are arranged on a single substrate of glass (orquartz) in an integrated form using thin-film transistor technology.Preferably, thin-film transistors are constructed from a thincrystalline silicon film.

In the circuit configuration of this embodiment, the active matrixregions 101-104 and their peripheral drive circuits are integrallyformed on one substrate. This configuration is advantageous in that itprovides substantial labor savings and production cost reductioncompared to conventional manufacturing methods, in which peripheralcircuits are constructed as integrated circuits (ICs) on a substrate andinterconnected by use of tape automated bonding (TAB) technology. Theconfiguration of the embodiment is also advantageous in that the overallconstruction can be reduced in size. As can be seen from FIG. 11, someof the peripheral circuits are integrally arranged with the individualactive matrix regions 101-104. This is particularly effective forenhancing the aforementioned advantages of this embodiment.

According to the present embodiment, the individual active matrixregions 101-104 can produce different images independently of oneanother. Operations of the individual active matrix regions 101-104 aresynchronously controlled by a common horizontal scanning control clocksignal (CLK H) and a common vertical scanning control clock signal (CLKV).

In the integrated liquid crystal panel 207 shown in FIG. 11, the activematrix regions 101 to 103 generate red, green and blue (RGB) colorimages, respectively, while the active matrix region 104 generates anentirely white image. A color image produced from the RGB colors and theentirely white image are superimposedly projected onto a common screen210, as will be described later.

FIG. 12 is a diagram showing the construction of a projection-type imagedisplay system 200 employing the integrated liquid crystal panel 207 ofFIG. 11. Referring to FIG. 12, white light (W) emitted from a lightsource 201 is reflected by mirrors 202 and 203 and falls upon the activematrix region 104 of the integrated liquid crystal panel 207. The activematrix region 104 is not required if it is needed to show a full-screenwhite image continuously. However, if it is desired to selectively hideaway a certain portion of an image produced by the active matrix regions101 to 103, it is essential to produce an overlapping white image by theactive matrix region 104.

On the other hand, white light emitted from a light source 212 isreflected by a mirror 213 in the direction of dichroic mirrors 204-206.The red (R), green (G) and blue (B) colors are separated from thereflected white light as the dichroic mirror 206 selectively reflectscomponents of a blue (B) light wavelength band, the dichroic mirror 205selectively reflects components of a green (G) light wavelength band,and the dichroic mirror 204 selectively reflects components of a red (R)light wavelength band.

The individual colors fall upon the integrated liquid crystal panel 207of which details are depicted in FIG. 11 and undergo specific opticalmodulation. Signals required for controlling the liquid crystal panel207 are fed from a control unit 211 to the liquid crystal panel 207.Individual images formed through optical modulation by the liquidcrystal panel 207 are polarized into specific states of polarization asthey pass through an optical unit 208.

The optical unit 208 incorporates polarizers for transforming the RGBimages into clockwise-rotating, circularly polarized beams. Each ofthese polarizers comprises a polarizing plate and a quarter-wave plate,or a polarizing plate, π-cell and a quarter-wave plate. Alsoincorporated in the optical unit 208 is a polarizer for transforming theentirely white image into a counterclockwise-rotating, circularlypolarized beam.

The red (R), green (G), blue (B) and white (W) images thus produced areprojected onto the screen 210 with one image superimposed on anotherthrough projection lenses incorporated in the optical unit 208.

FIG. 13 is a timing chart describing operation for presenting imageswith the projection-type image display system of FIG. 12. As noted inFIG. 13, light beams for projecting the RGB images generated by theactive matrix regions 101 to 103 are circularly polarized with clockwiserotation by the optical unit 208 and superimposed on one another to forma combined color image A on the screen 210.

On the other hand, the white image generated by the active matrix region104 is circularly polarized with counterclockwise rotation by theoptical unit 208 and superimposingly projected upon the RGB images onthe screen 210.

If a viewer looks at the screen 210 with the naked eye, the screen 210will be entirely white because the RGB images are masked by the whiteimage. If the viewer looks at the screen 210 through an optical filterwhich selectively allows clockwise-rotating, circularly polarized lightto pass through, it would be possible to see the color image A becausethe counterclockwise-rotating, circularly polarized white image isalmost completely interrupted. This can be achieved by wearing adedicated viewing device incorporating optical filters which selectivelyallow clockwise-rotating, circularly polarized light to pass through,for instance.

The image display system of this embodiment makes it possible to enableonly those viewers who wear such a dedicated viewing deviceincorporating the optical filters to see the color image A whilepresenting the entirely white image, containing no visual information,to other viewers who looks at the screen 210 with the naked eye.

Although the color image A is entirely masked by the white imageaccording to this embodiment, it may be modified in such a way that thewhite image overlap part of the color image A. Moreover, the overlappingimage need not necessarily be white, but may be of any color which wouldbe found to be effective for hiding away an underlying image by way ofexperiments.

The aforementioned construction of this embodiment can be used forconveying visual messages to concerned personnel only by use of videoscreens which can be seen by the general public. Potential applicationsof this kind would be found in various industrial fields, includingairports, railway stations, shopping centers, and so forth. What isrequired for intended recipients of such messages is to wear specialviewing devices capable of allowing light having a specific state ofpolarization to pass through when they look at the screen 210.

Operation of the liquid crystal panel 207 of FIG. 11 is now brieflydescribed. The following discussion focuses on the operation of theactive matrix region 101 for the simplicity of explanation. It is to benoted that the other active matrix regions 102-104 operate in a similarway to the active matrix region 101.

Referring to FIG. 11, designated by the numerals 110, 111 and 112 areflip-flop circuits, each of which can assume two stable states. As anexample, if a rising edge of the horizontal scanning control clocksignal CLK H enters the flip-flop circuit 111 when its input (point X₀)is set to H (logic high) and its output (point X₁) is set to L (logiclow), the output of the flip-flop circuit 111 turns to H, or an H levelappears at point X₁. This state is maintained until another rising edgeof the clock signal CLK H enters.

On the contrary, if a rising edge of the clock signal CLK H enters theflip-flop circuit 111 when its input is set to L and its output is setto H, the output of the flip-flop circuit 111 turns to L. If a risingedge of the clock signal CLK H enters the flip-flop circuit 111 whenboth of its input and output are set to L, the output of the flip-flopcircuit 111 remains L.

First, a rising edge of the vertical scanning control clock signal CLK Venters the flip-flop circuit 112 of the vertical scanning controlcircuit 106. At this point, the clock signal CLK V makes a horizontalscanning timing enable signal H STA effective.

Specifically, when the rising edge of the CLK V signal enters theflip-flop circuit 112 in a condition where an H level of the H STAsignal is applied to an input of the flip-flop circuit 112, the outputof the flip-flop circuit 112 becomes H. As a result, the signal level ofline Y₀ is set to H, and this causes thin-film transistors of individualpixels in line Y₀, denoted by addresses (0, 0), (1, 0), . . . , (m, 0),to become all ON.

As the rising edge of the horizontal scanning control clock signal CLK Henters the flip-flop circuit 110 in this condition, the horizontalscanning timing enable signal H STA is made effective. As a result, thesignal level at point X₀ is set to H.

Since inputs of the flip-flop circuits 111 and onward are all at an Llevel when the rising edge of the clock signal CLK H has just entered,outputs of the flip-flop circuits 111 and onward are all at an L levelin this condition.

As an image sampling signal line 116 become an H level in theaforementioned condition, a sample hold circuit 114 acquires image dataB, and signals corresponding to such image data flows in an image signalline 117. More specifically, specific image signals are applied tosource electrodes of thin-film transistors of individual pixels denotedby addresses (0, 0), (0, 1), . . . , (0, n). Since the thin-filmtransistors of the pixels denoted by addresses (0, 0), (1, 0), . . . ,(m, 0) are all ON in this condition, image information is written intothe pixel designated by address (0, 0) only.

Next, a succeeding rising edge of the clock signal CLK H causes theoutputs of the flip-flop circuits 110 and 111 to become L and H,respectively. The signal level at point X₁ is set to H. In thiscondition, all points denoted by X_(m), excluding point X₁, are set toL. As a result, a sample hold circuit 115 acquires specific image dataand image information is written into address (1, 0).

Image information for addresses (0, 0) through (m, 0) is sequentiallywritten in synchronism with the clock signal CLK H in this way.

When the image information for line Y₀ has been fully written into therespective addresses, the output of the flip-flop circuit 112 becomes Lat a succeeding rising edge of the clock signal CLK V and the output ofa flip-flop circuit 113 becomes H. Then, image information for line Y₁is written into relevant addresses following the same sequence asdescribed above. Image information for individual pixels is sequentiallywritten line by line in this manner, and image presentation for oneframe is finished when address (m, n) is reached. Frames are refreshedat 30 Hz, for instance, to continuously present an on-screen image.

Seventh Embodiment

A seventh embodiment of the invention described below is characterizedin that it has basically the same construction as the sixth embodimentbut employs an integrated liquid crystal panel as shown in FIG. 14instead of the liquid crystal panel 207. Compared to the liquid crystalpanel 207 of FIG. 11, the liquid crystal panel of FIG. 14 has anexpanded circuit configuration and can produce two sets of RGB colorimages as well as two overlapping entirely white images at the sametime.

According to the configuration of FIG. 14, a horizontal scanning controlcircuit 409 controls horizontal scanning operation in active matrixregions 401 to 404 while a horizontal scanning control circuit 410controls horizontal scanning operation in active matrix regions 405 to408.

On the other hand, a vertical scanning control circuit 411 controlsvertical scanning operation in the active matrix regions 401 and 405, avertical scanning control circuit 412 controls vertical scanningoperation in the active matrix regions 402 and 406, a vertical scanningcontrol circuit 413 controls vertical scanning operation in the activematrix regions 403 and 407, and a vertical scanning control circuit 414controls vertical scanning operation in the active matrix regions 404and 408.

The liquid crystal panel thus constructed can be used as ahigh-brightness display screen or for producing a three-dimensionalimage, for instance. Each of the horizontal and vertical scanningcontrol circuits 409-414 controls a plurality of active matrix regionsin this embodiment. This arrangement offers such advantages as compactdesign, improved productivity and higher reliability.

Eighth Embodiment

An eighth embodiment of the invention has basically the sameconstruction as the sixth embodiment but its active matrix regions 101to 103 are used to produce a common black-and-white image. Thisembodiment makes it possible to obtain an extremely bright image asthree independently generated images are superimposed on one another,although they are black-and-white.

In the construction of the image display system shown in FIG. 14,semitransparent mirrors should substitute for the dichroic mirrors204-206 to achieve high brightness. Alternatively, separate lightsources may be provided at positions corresponding to the active matrixregions 101 to 103 of the liquid crystal panel 207.

Ninth Embodiment

A ninth embodiment of the invention has basically the same constructionas the sixth embodiment but employs simple polarizing plates as meansfor creating specific states of polarization. The polarizing plates ofthis embodiment should be able to linearly polarize white and colorimages in two mutually perpendicular planes of polarization. It shouldbe appreciated that this approach serves to simplify the construction ofthe means for creating specific states of polarization and of opticalfilters which selectively allow polarized light having the specificstates of polarization to pass through.

1. An image display system constructed in such a way that a first imagehaving a first state of polarization and a second image having a secondstate of polarization are projected with one image superimposed onanother, wherein said first image is entirely white.